In 2012, that statement was used to put his struggles at Double-A Jackson in context. This season, though, it’s more of a testament to how much the right-hander has improved over the last year.

Opening the year back in Double-A, it took Walker just 14 starts to master the level. After registering a 2.46 ERA and .195 BAA with 96/30 K/BB in 84 innings at the level, the Mariners offered their top prospect a well-deserved promotion to Triple-A Tacoma.

Obviously he made a strong impression during his Triple-A debut on Tuesday night, as the right-hander allowed three hits and two walks over six scoreless innings while notching four strikeouts.

The Mariners don’t want to overexpose Walker in the Pacific Coast League—and especially following his overwhelming success in Double-A—so there’s a realistic chance he sees some time in the major leagues later this season. The only things that may prevent that from happening is a poor showing at Triple-A Tacoma or an innings limit implemented by the organization.

Here’s a look at the rest of the hottest and coldest pitchers at every minor league level.

Rookie/Short Season

Drafted by the Cubs at No. 56 overall in 2012, Blackburn has opened the season with a pair of impressive starts in the Northwest League and could conceivably finish the year at a full-season level.

Luiz Gohara, LHP, Seattle Mariners

4 IP, 6 H, ER, 5 K (1 GS)

The 6’3”, 210-pound left-hander was outstanding in his professional debut on Friday. Oh yeah, he’s only 16.

Edwin Diaz, RHP, Seattle Mariners

11 IP, 4 H, 14/1 K/BB (2 GS)

A third-round draft pick in 2012 out of Puerto Rico, Diaz, 19, posted a 5.21 ERA with 20/17 K/BB last season over 19 innings in the Arizona League; the 6’2” right-hander has been nearly unhittable through his first two starts in the Pioneer League.

*Coldest pitchers will be included once more prospects are active at both levels.

Low-A

Selected by the Tigers with their first pick (third round) in the 2012 draft, Thompson was shelled in his first two starts for Low-A West Michigan; the last two have been significantly better: 11 IP, 5 H, 2 ER, 17/2 K/BB.

Tyler Glasnow, RHP, Pittsburgh Pirates

62.1 IP, 2.60 ERA, .153 BAA, 95/37 K/BB (14 GS)

To put it simply: Glasnow has been a monster this season at Low-A West Virginia; the 6’7” right-hander will endure bouts of inconsistency where his arm and body get out-of-sync; he’s allowed more walks (37) than hits (33) with a 13.8 K/9 rate through 14 starts; last two starts: 10 IP, 10 H, ER, 15/2 K/BB.

Lance McCullers, RHP, Houston Astros

65.2 IP, 1.92 ERA, .210 BAA, 75/28 K/BB (17 G/11 GS)

McCullers has been excellent to begin his full-season debut, showing the ability to both miss bats and generate weak contact with a plus fastball-curveball combination and developing changeup; last two starts: 10 IP, 7 H, ER, 13/2 K/BB.

Walker Weickel, RHP, San Diego Padres

55.1 IP, 4.55 ERA, .267 BAA, 42/22 K/BB (12 G/11 GS)

The 2012 supplemental first-rounder struggled over the first two months of the season but has seemingly turned the corner over his last two starts: 10.1 IP, 4 H, 14/0 K/BB.

C.J. Edwards, RHP, Texas Rangers

71 IP, 2.03 ERA, .177 BAA, 92/27 K/BB (14 GS)

The wiry-thin right-hander’s stuff has taken a big step forward this season, and he should receive a promotion to High-A sometime in the near future; last four starts: 18.2 IP, 8 H, 33/8 K/BB.

Miguel Almonte, RHP, Kansas City Royals

73.2 IP, 3.42 ERA, .245 BAA, 77/26 K/BB (14 GS)

The 20-year-old has a lightning quick arm and the potential for three above-average-to-plus offerings at maturity; Almonte turned in his best start of the season on Tuesday against a powerful Low-A Hickory offense: 7.2 IP, 7 H, 12/0 K/BB. Here’s some game video of the right-hander that I filmed on May 7.

Chris Anderson, RHP, Los Angeles Dodgers

2 IP, H, 5 K (1 GS)

The Dodgers’ first-round pick was sharp in his professional debut on Tuesday, allowing one hit with five strikeouts over two scoreless frames.

Lucas Sims, RHP, Atlanta Braves

51.1 IP, 2.98 ERA, .200 BAA, 60/18 K/BB (16 G/6 GS)

Sims struggled with his command over the first month of the season but has been very impressive since the start of May; last 10 appearances: 40 IP, 2.03 ERA, .205 BAA, 53/8 K/BB.

Taylor Guerrieri, RHP, Tampa Bay Rays

59 IP, 2.29 ERA, .221 BAA, 47/11 K/BB (12 GS)

After possibly the worst start of his professional career on June 2 (4 IP, 11 H, 6 ER), Guerrieri has been dominant over his last three outings: 16 IP, 11 H, 13/4 K/BB.

Coldest

Nick Travieso, RHP, Cincinnati Reds

21 IP, 5.57 ERA, .329 BAA, 12/9 K/BB (5 GS)

After logging only 21 innings in the Arizona League last summer, the Reds surprisingly bumped Travieso to Low-A to begin the season. The hard-throwing right-hander is too raw and lacks the necessary consistency for the level; it’ll be interesting to track whether the organization lets him work through his struggles or sends him back to a rookie league.

Dillon Maples, RHP, Chicago Cubs

26.2 IP, 8.10 ERA, .248 BAA, 27/26 K/BB (8 G/7 GS)

Maples offered a glimpse of his potential during his start on June 3 (5 IP, 2 H, 7/3 K/BB) but has been painfully inconsistent in all other outings.

High-A

Owens had arguably his best start of the season on Tuesday, as he allowed three hits and a walk over seven scoreless frames while fanning six batters. More importantly, as noted by Jake Seiner of MiLB.com, the 6’6” left-hander did it with general manager Ben Cherington in attendance.

Eddie Butler, RHP, Colorado Rockies

88.1 IP, 2.24 ERA, .174 BAA, 85/34 K/BB (15 GS)

After dominating at Low-A Asheville to begin the season, Butler has been equally impressive since his promotion to the hitter-friendly California League. Through six High-A starts: 34 IP, 3.18 ERA, .226 BAA, 34/9 K/BB.

Kyle Crick, RHP, San Francisco Giants

13.2 IP, 0.66 ERA, .255 BAA, 22/12 K/BB (4 GS)

Sidelined since mid-April with an oblique strain, the Giants’ top prospect was outstanding in his return to the mound on Friday: 4 IP, 3 H, 10/3 K/BB.

Andrew Heaney, LHP, Miami Marlins

30.1 IP, 1.19 ERA, .198 BAA, 36/10 K/BB (7 G/6 GS)

The 6’2” left-hander has good command of a deep arsenal and an underrated feel for pitching; has allowed four earned runs through 30.1 innings this season; expect him to move quickly.

I really don’t know what to say about Zimmer’s struggles this season, but from what I’ve seen, he hasn’t grasped how to get opposing hitters to expand the strike zone and therefore leaves entirely too many pitches over the plate. There have also been times when his stuff seems softish and light

Jed Bradley, LHP, Milwaukee Brewers

68.1 IP, 4.21 ERA, .273 BAA, 53/37 K/BB (14 GS)

Expected to move quickly when the Brewers selected him in the first round of the 2011 draft, Bradley is currently pitching in the Florida State League for the second consecutive season.

Mark Sappington, RHP, Los Angeles Angels

83.2 IP, 4.20 ERA, .246 BAA, 69/41 K/BB (15 GS)

Even though the 6’5” right-hander boasts a plus fastball, his lack of command and fringy secondary offerings have led to a shaky full-season debut; last 10 starts: 55 IP, 5.56 ERA, 56 H, 40/32 K/BB.

Garrett Gould, RHP, Los Angeles Dodgers

71.2 IP, 7.03 ERA, .295 BAA, 55/28 K/BB (15 G/14 GS)

I think it’s time the Dodgers gave Gould a break from the California League, no? Last three starts: 13.1 IP, 23 H, 18 ER, 12/5 K/BB.

Double-A

The 6’6” right-hander creates excellent plane on his fastball and has furthered the progress he made last season with his secondary offerings; first Double-A start: (W) 6 IP, 5 H, 2 ER, 7/1 K/BB.

Anthony Ranaudo, RHP, Boston Red Sox

79 IP, 2.28 ERA, .180 BAA, 86/27 K/BB (14 GS)

The 2010 first-rounder has been one of the more impressive (and consistent) pitchers in the high minors this season, and could get a look in the major leagues later this season under the right circumstances.

Mike Foltynewicz, RHP, Houston Astros

74 IP, 2.55 ERA, .237 BAA, 78/37 K/BB (19 G/11 GS)

Foltynewicz has been one of the more talked-about pitching prospects in the minors this season thanks to a jump into the elite velocity range and improved command. Since his promotion to Double-A: 48 IP, 1.88 ERA, .202 BAA, 49/23 K/BB (12 G/6 GS)

Marcus Stroman, RHP, Toronto Blue Jays

31 IP, 3.77 ERA, .248 BAA, 33/9 K/BB (7 GS)

Stroman, a 5’9” right-hander, attacks hitters with a plus fastball and breaking ball, as well as a changeup with above-average potential. The Blue Jays will develop him as a starter, but don’t be surprised if he’s coming out of the major league bullpen in August and September. Last four starts: 21 IP, 13 H, 4 ER, 20/4 K/BB.

Coldest

Brody Colvin, RHP, Philadelphia Phillies

38 IP, 6.87 ERA, .270 BAA, 16/23 K/BB (11 G/6 GS)

After posting an 11.02 ERA over seven starts for Double-A Reading last season, Colvin has been a bit better this season—but not by much. Last 10 appearances: 32.2 IP, 7.16 ERA, 14/21 K/BB.

Donn Roach, RHP, San Diego Padres

76.2 IP, 4.34 ERA, .288 BAA, 2.44 GO/AO, 48/31 K/BB (15 GS)

Roach still boasts the power sinker that led to a breakout performance across two levels last season, but hasn’t commanded it as well this season back at Double-A San Antonio. Oddly, he’s also allowed exactly 10 hits in three of his last 10 starts. I know—weird.

After getting a taste of the major leagues out of the Cardinals' bullpen, Martinez was optioned to Triple-A Memphis where he’s been outstanding as a starter: 29.2 IP, 1.82 ERA, .223 BAA, 29/9 K/BB (6 GS).

Erik Johnson, RHP, Chicago White Sox

90.2 IP, 2.18 ERA, .193 BAA, 80/26 K/BB (15 GS)

Basically the only promising pitching prospect in the White Sox’s system, Johnson had a strong showing in his Triple-A debut on Sunday: 6 IP, 5 H, ER, 6/5 K/BB.

Taijuan Walker, RHP, Seattle Mariners

90 IP, 2.30 ERA, .191 BAA, 100/32 K/BB (15 GS)

Having already mastered the Southern League this season in his second tour of the level (Double-A), it was fitting that the 20-year-old right-hander dominated in his Triple-A debut on Tuesday: (W) 6 IP, 3 H, 4/2 K/BB.

Coldest

Ethan Martin, RHP, Philadelphia Phillies

78.2 IP, 5.03 ERA, .246 BAA, 73/49 K/BB (15 GS)

Acquired from the Dodgers last year at the trade deadline, the Phillies bumped Martin up to Triple-A this season where’s struggled mightily with his control: 49 walks in 78.2 innings.

Tyler Thornburg, RHP, Milwaukee Brewers

74.2 IP, 5.79 ERA, .297 BAA (11 HR), 87/29 K/BB (15 GS)

Thornburg is still missing his share of bats, but too many balls left up in the zone—and struggle to repeat his plane with consistency—has led to 90 hits (11 home runs) in only 74.2 innings.

Chris Heston, RHP, San Francisco Giants

93.1 IP, 5.30 ERA, .296 BAA, 86/36 K/BB (16 GS)

Coming off a breakout campaign in 2012 during which he posted a 2.24 ERA and .230 BAA with 135 strikeouts in 148.2 innings, Heston’s ground-ball and walk rates are trending in the wrong direction, though he’s still missing a favorable number of bats.